I tested a new solenoid valve that RJ gave me. It is a two way control solenoid valve, which means it has two solenoid one it. This new solenoid valve reacts very fast, I love that sound when it was working–powerful.

However, besides the fast reaction, this new solenoid valve is very the same as the old one in the sense of control–as shown in the video, the only way that controls the pneumatic rod maintaining in a particular position is let it vibrates in a high frequency around that position (name this method “vibration method”).

A big problem with this system is: uncertainty. With the same input to the pneumatic cylinder, it results different rod positions! This shown that the system is time varying. Thus, using “vibration method” is definitely a bad idea.

Therefore, it is necessary to change the hardware:

B and B’ are solenoid control valves. When B apply air pressure and B’ exhaust air, the rod moves forward; wen B’ apply air pressure and B exhaust air, the rod moves backward; when both B and B’ apply air pressure, the rod will stand still.

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